Mesenchymal cystic hamartoma of the lung.

Mesenchymal cystic hamartoma, although first reported as early as 1980s, remains a very rare lung disease. There have been less than 20 cases reported to date. Mesenchymal cystic hamartoma usually has an indolent course, but it could potentially result in morbidity and mortality. Biopsy is needed to confirm the diagnosis because it is essential to rule out other possibilities including malignancy.